1. Field of the Invention
The present invention relates to telecommunications in general, and, more particularly, to a wireless telecommunications system.
2. Description of Related Art
FIG. 1 depicts a schematic diagram of a portion of a known wireless telecommunications system, providing wireless telecommunications service to a number of wireless mobile units (e.g., wireless mobile units 101-1 through 101-3) that are situated within a geographic region. The heart of a typical wireless telecommunications system is a wireless switching center (“WSC”) 120. Typically, the WSC 120 is connected to a plurality of base stations (e.g., base stations 103-1 through 103-5) that are dispersed throughout the geographic region serviced by the system and to the local and long-distance telephone and data networks (e.g., local-office 130, local-office 138 and toll-office 140). WSC 120 is responsible for, among other things, establishing and maintaining a call between a first wireless mobile unit and a second wireless mobile unit or, alternatively, between a wireless mobile unit and a wireline mobile unit (e.g., wireless mobile unit 150), which is connected to the system via the local and/or long-distance networks.
The geographic region serviced by a wireless telecommunications system is partitioned into a number of spatially distinct areas called “cells.” As depicted in FIG. 1, each cell is schematically represented by a hexagon. In practice, however, each cell has an irregular shape that depends on the topography of the terrain surrounding the cell. Typically, each cell contains a base station, which comprises the radios and antennas that the base station uses to communicate with wireless mobile units in that cell and also comprises the transmission equipment that the base station uses to communicate with the WSC 120. However, locating wireless mobile units within a cell was often difficult.
Prior art FIG. 2 illustrates a base station 203 and the typical coverage area of a three sector antenna typically utilized on a base station 203. Since the base station antenna typically has three sectors (which are typically 3 separate antennas), each of the three sectors covers about a 120° area of the cell 205. These three sectors, labeled 207a, 207b, and 207c each correspond to one of the three sector antennas of base station 203.
When a wireless mobile unit 210, shown being utilized in a car in FIG. 2 for example, it is turned on, the nearest cell site or base station such as base station 203 becomes aware of its location in terms of antenna face or sector direction. Thus, the base station 203 is not only aware of wireless mobile unit 210, but it is also aware that the wireless mobile unit 210 is within a particular sector of its coverage region, such as sector 207a. Hence, the base station 203 knows the approximate geographic location of wireless mobile unit 210. This method of locating a wireless mobile unit 210 requires only one cell site or base station 203, although the area covered by the sector could be quite large.
Prior art FIG. 3 depicts a known triangulation technique for locating the wireless mobile unit 310. Using this triangulation technique, three base stations 303a, 303b, and 303c are used to pinpoint the location of wireless mobile unit 310. A propagation delay between the wireless mobile unit 310 sending a message to each of the three base stations 303a, 303b, and 303c is used to determine the distance to the wireless mobile unit 310, such as distance X, distance Y and distance Z as shown in prior art FIG. 3. Triangulation requires the cell sites to be synchronized to a reference clock so when the wireless mobile unit 310 contacts each of base stations 303a, 303b, and 303c, a time stamp of when the message was received is created. Then, the time stamps are compared and used to determine the exact location using radio wave propagation characteristics and some rudimentary mathematics. This method requires three cell sites for accurate positioning.
Further, global positioning systems (GPS) have recently been developed to the point where they are cheap to implement. Thus, such systems may soon be prevalent in wireless mobile units to determine the precise location thereof. In addition, in an area of wireless technology, assisted GPS is being developed to improve on normal GPS for position or location detection of wireless mobile units. In addition, other position determining systems are constantly being developed. Thus, with all these various ways being developed to locate a wireless mobile unit and to pinpoint the location of the wireless mobile unit, a need exists to create other uses for the location or position information of wireless mobile units.
Further, as wireless units, such as those in cars for example, travel from region to region a user might find information specific to the particular region to be quite useful. For example, weather warnings, traffic problems or other road problems, if received by the user, would allow the user to take appropriate action. Knowing about traffic accidents on major highways or roads closed for construction would enable the user to find an alternate route to avoid the problem. Thus, a need exists for getting region-specific information to a user.